Since the physical chemical properties of (minus)- and (plus)-isomers of sympathetic amines are the same, these agents provide a valuable tool to study the adrenergic receptors. The project is directed towards previously unanswered questions related to alpha adrenergic receptors. The study will be aimed at obtaining the dissociation constants of stereoisomers of catecholamines. In addition, an alpha adrenoreceptor blocker with high specific activity will be obtained and its pharmacological and biochemical binding characteristics in the microsomes from blood vessels will be studied. Although the existence of alpha adrenoreceptors is also postulated in the nerve terminal, the stereochemical characteristics of these receptors remains to be studied. Thus, the project will also be directed towards investigating the stereoselectivity of these sites in the nerve terminal. Understanding the nature of these receptors in the nerve terminal and tissue may be of vital importance in understanding the mode of action of antihypertensive drugs. Bibliographic references: Drug-receptor-related stereoselectivities in fat cells. DeSantis, L.M., Feller, D.R., and Patil, P.N. Europ. J. Pharmacol. 28, 302-309 (1974). A Review, Molecular geometry and adrenergic drug activity, Patil, P.N., Miller, D.D., and Trendelenburg, U. Pharmacol. Rev. 26, 323-392 (1974).